System and method for controlling a blowout location at an offshore oilfield

ABSTRACT

A system for controlling a blowout location at an offshore oilfield comprises:
         a support construction that is movable next to a blowout location in an offshore oilfield and that can be set to rest in seabed, the support construction comprising:
           a) a first foundation part and a second foundation part that are located at a distance from each other;   b) support members that are located at a distance from each other; and   
           a funnel structure that is movable along the support members, the funnel structure comprising connecting members that are form-locking with the support members.       

     The first foundation part, the second foundation part and the support members are so configured that the blowout location can be restricted a) between the first foundation part and the second foundation part and b) between the support members. The funnel structure a) is movable along the support members from a side position to above the blowout location and b) is dimensioned to restrict the blowout by redirecting flow from the blowout into an exit pipe. The funnel structure and the support construction are so dimensioned that when the funnel structure is located on top of the blowout location, the system remains substantially stable to enable restricting the blowout. Includes an independent patent claim for a method for controlling a blowout location at an offshore oilfield.

FIELD OF THE INVENTION

The invention relates to systems and methods for controlling a blowoutlocation at an offshore oilfield.

BACKGROUND ART

Drillings in seabed oil wells have been carried out since some time.When seabed oil is drilled, in order to avoid causing excessive damageto sea life, it is necessary to utilize reliable pressure controlsystems that have developed since 1920s and thereafter. Now we know thatoil or gas gushers which may appear in offshore drilling—despite ofknown pressure control systems—are difficult to control.

The Deepwater Horizon oil spill, also known as Gulf of Mexico oil spill,is a massive and—at the time of writing still ongoing—oil spill in theGulf of Mexico. The spill originates from a blowout, i.e. uncontrolledrelease of crude oil and/or natural gas from an offshore oil well afterpressure control systems have failed.

In the Deepwater Horizon case, the oil rig's blowout preventionmechanism which was designed as a fail-safe device fitted at the sourceof the well did not automatically cut off the oil after the explosion atthe oil rig. The operator of the oil rig attempted to use remotelyoperated underwater vehicles to close the blowout preventer valves onthe well head but did not have a remarkable success.

Next, the operator tried to control the oil spill by placing a 125-tonnecontainer dome over the largest of the leaks and then to pipe the oil toa storage vessel on the surface. It could be that this arrangementfailed when gas leaking from the pipe combined with cold water to formmethane hydrate crystals which may have blocked up the steel canopy atthe top of the dome. It could be that the excess buoyancy of thecrystals clogged the opening at the top of the dome which is thelocation where the riser should have been connected.

SUMMARY OF THE INVENTION

It is an object of the invention to enable controlling a blowoutlocation at an offshore oilfield such as what might be necessary after,say, a fail-safe device has failed, or when a pipe between an offshoreoilfield and a collection tank has broken.

This object can be achieved with a system according to claim 1, and witha method according to claim 9.

The system for controlling a blowout location at an offshore oilfieldcomprises a support construction that is movable next to a blowoutlocation in an offshore oilfield and that can be set to rest in seabed,the support construction comprising a) a first foundation part and asecond foundation part that are located at a distance from each other,and b) support members that are located at a distance from each other,and the system further comprises a funnel structure that is movablealong the support members, the funnel structure comprising connectingmembers that are form-locking with the support members.

In the system, the first foundation part, the second foundation part andthe support members are so configured that the blowout location can berestricted a) between the first foundation part and the secondfoundation part and b) between the support members. Furthermore, thefunnel structure a) is movable along the support members from a sideposition to above the blowout location and b) is dimensioned to restrictthe blowout by redirecting flow from the blowout into an exit pipe. Thefunnel structure and the support construction are so dimensioned thatwhen the funnel structure is located on top of the blowout location, thesystem remains substantially stable to enable restricting the blowout.

The method for controlling a blowout location at an offshore oilfieldcomprises the steps of a) bringing a system for controlling a blowoutlocation at an offshore oilfield to an offshore oilfield, b) positioningthe first foundation part and the second foundation part of the systemto rest in seabed at opposite positions around the blowout location, c)attaching a funnel structure in a form-locked manner to the system at anaway position from the blowout location, d) moving the funnel structurealong support members of the system until the funnel structure is on topof the blowout location, and e) controlling the blowout location byredirecting flow from the blowout with the funnel structure into an exitpipe.

The dependent claims describe advantageous aspects of the system and ofthe method.

ADVANTAGES OF THE INVENTION

The inventor believes that a system of the above kind is easierpositionable in place than the 125-tonne container dome since the massflow from the blowout must have exerted a gigantic momentum on the dome,which thus must have been extremely difficult to bring in place. Inaddition, the inventor believes that by using this kind of system theadverse effect observed in the 125-tonne container dome experiment,where gas leaking from the pipe combined with cold water to form methanehydrate crystals, can be better avoided.

Since in the method, the first foundation part and the second foundationpart are first brought to rest on seabed before the funnel structure andbecause the funnel structure is form-locked to the support membersbefore the funnel structure is positioned to restrict the flow, the flowfrom the outblow causes inertia on the funnel structure only when thefunnel is positioned very stable in system and kept in place by thefirst foundation part and the second foundation part. If now the firstfoundation part and the second foundation part are stable enough as theymust, the funnel structure can be positioned on top of the outblow muchcloser to the outblow location and, even more importantly, much moreprecisely than a 125-tonne container dome that was floating in thewater.

Any of the first foundation part and second foundation part, or both,may comprise at least one compartment that is fillable with ballast. As“ballast” is here meant a material or a composition of several materialsthat over a predetermined period of time remains substantially stable insea water and that has a density much larger than water. Examples ofsuch materials or components of the composition include but are notlimited to metals—especially iron or lead, stone—especially granite,concrete, and sand. With the at least one compartment, the dead mass ofthe respective foundation part can be increased when the foundation partis in place. In this manner, the first and the second foundation partcan be set rest in seabed stable enough while the foundation parts beingstill lightweight enough for easier carriage to the offshore oilfield.

The support members may be rod-like members around which the funnelstructure form-locks. Thanks to this solution, the distance between thefirst and second foundation part does not need to be known precisely inadvance. Sometimes the seabed may cause the foundation parts slightlymove when they set to rest in place which makes a precise positioningdifficult and to depend on exact seabed characteristics.

The support members may be adapted to run between holders at the firstfoundation part and the second foundation part. This is a particularlyelegant solution since it enables the support members to be transportedindependently of the first foundation part and the second foundationpart.

The support members may be elongated guide members which form-lock withthe funnel structure.

Each of the support members may be arranged to run along the respectivefoundation part.

If the funnel structure comprises a vertically movable funnel, it ispossible to lower the funnel to cover the outblow location only afterthe funnel structure is supported by the system. In this manner, thesystem does not need to be installed very close to the outblow locationwhich is believed to make the installation work easier.

If the system further comprises adjusting members to adjust the heightof the support members from the seabed, the system can be used forblowouts at different heights from seabed.

LIST OF DRAWINGS

In the following, the preferred embodiments of the system and method aredescribed in more detail with reference to the examples shown in theaccompanying drawings, of which:

FIG. 1 shows the support structure of a system for controlling a blowoutlocation at an offshore oilfield, without the funnel structure andsupport members;

FIG. 2 shows the system of FIG. 1 with support members and funnelstructure installed;

FIG. 3 shows the system of FIG. 2 when the funnel structure is placed ontop of the blowout location;

FIG. 4 illustrates the system of FIG. 2 as seen from the left side;

FIG. 5 illustrates the moving of the funnel structure from the positionshown in FIG. 2 to the position shown in FIG. 3, as seen from the leftside;

FIG. 6 illustrates the step of lowering the funnel structure, as seenfrom the left side;

FIG. 7 a further embodiment of the system as seen from an end;

FIG. 8 the system of FIG. 7 as seen from top;

FIG. 9 a further embodiment of the system as seen from an end; and

FIG. 10 a further embodiment of the system as seen from top.

Same reference numerals refer to similar technical features in alldrawings.

DETAILED DESCRIPTION

FIG. 1 shows a system for controlling a blowout location 102 at anoffshore oilfield. The blowout location 102 is under water in a sea 100.From the blowout location 102, a stream 110 consisting of a mixture ofoil, gas, water and sand gushes upwards. In FIG. 1, the blowout location102 is shown as the end 103 of a cut pipe. In reality, the blowoutlocation 102 could be instead of or in addition to a cut pipe also atorn or otherwise damaged pipe, or some other structure. In deep seainstallations suffering from a blowout, no pipe nor pipe end may bevisible; the blowout location may be buried in mud or sand in the seabed 101.

The system for controlling a blowout location 102 comprises a supportconstruction. The support construction comprises a first foundation part150 and a second foundation part 150. The first and second foundationparts 150 are brought to an offshore oilfield.

Then the first foundation part 150 and the second foundation part 150are positioned to rest in seabed 101 at opposite positions around theblowout location 102, which then in a sense is so restricted betweenthem. The distances between the blowout location 102 and the firstfoundation part 150 and the second foundation part 150 have been denotedwith F and G, respectively. The first foundation part 150 and the secondfoundation part 150 are thus located at a distance F+G from each other.Distances F and G are preferably chosen so large that the stream 110does not disturb the installation of the support construction.

Each of the first foundation part 150 and the second foundation part 150comprises holders 151 for support members. The holders 151 are locatedat a distance A from each other. The holders 151 are in FIG. 1 shown aseyes having a receiving opening 152 for a support member. The holders151 are preferably form-locked to the first or the second foundationpart 150, respectively. The distance between the holders 151 of thefirst foundation part 150 and the second foundation part 150 has beendenoted with B in FIG. 1.

The height and direction of the holders 151 with respect to a centralportion 154 of the first and second foundation part 150 may beadjustable. The adjusting can be achieved, for example, by adapting thelength and attaching angle of a connecting pile 153 between the centerpart and the holder 151. This enables the adjusting of the position ofthe holders 151 to compensate for the topology of the seabed.

The first foundation part 150 and the second foundation part 150 maycomprise at least one compartment 155 for receiving ballast. Thecompartments 155 of the foundation part 150 on the left hand side areshown empty while the compartments of the foundation part 150 on theright hand side are shown filled. Filling the compartments increases thedead mass of the first and second foundation parts 150 and thus makesthe system more stable.

If need be, the first foundation part 150 and the second foundation part150 may be extended by adding one or more extension modules 190 asillustrated by the dashed line in FIG. 1.

If need be, for further stability, the system can be anchored to theseabed 101 using anchors 180 or other suitable means.

FIG. 2 shows the system of FIG. 1 with support members 201, such assuitably selected beams, and funnel structure 250 installed. Thedistance between the elongated support members 201 has been denoted by a(a<A). The two distances a and A are preferably chosen so that, whilethe stream 110 from the blowout location 102 gets broader withincreasing height, the installation of the support members 201 is notdisturbed by the stream 110. Since the stream 110 preferably passesbetween the support members 201, the stream 110 in a sense getsrestricted between the support members 201.

The funnel structure 250 is installed so that it form-locks with thesupport members 201. The pedestal 254 of the funnel structure 250 maytherefore comprise eyes through which the support members 201 can pass.When the support members 201 are at both ends supported by the holders151 that are firmly in place at the first foundation part 150 and thesecond foundation part 150 (through receiving openings 152), the funnelconstruction 250 is very stable but can nevertheless be moved along thesupport members 201.

The width of the funnel structure 250 has been denoted by b in FIG. 2.The distance G between the blowout location 102 and the secondfoundation part 150 is preferably chosen so that the remaining clearancec between the stream 110 from the blowout location 102 and the funnelstructure 250 enables assembling the funnel structure in place withoutthe stream 110 disturbing the assembling procedure.

The funnel structure 250 comprises a sleeve 253 and a funnel 251.Preferably at the top end of the funnel 251 there is an opening 252 foran exit pipe. The skilled person understands that to fix the exit pipein place at funnel 251 or sleeve 253 there may be fittings required;they have been omitted from FIG. 2 for the sake of clarity.

FIG. 4 illustrates the system of FIG. 2 as seen from the left side. Theexit pipe 301 is mounted on the funnel 251 and preferably fixed at thesleeve 253 as illustrated by the dashdotted line in FIG. 3. Then thefunnel structure 250 is moved from the position shown in FIG. 2 to theposition shown in FIG. 3, as illustrated by arrow X in FIG. 5.

The funnel 251 in the funnel structure 250 is vertically movable. Thismeans, the funnel 251 is, as soon as it is on top of the blowoutlocation 102, lowered from its initial position as illustrated in FIGS.3 and 6 by arrow H so that it redirects the stream 110 comprising theflow from the blowout location 102 into the exit pipe 301.Alternatively, it is possible to lower the funnel 251 before it is movedon top of the blowout location 102. In this manner, the lowering of thefunnel 251 may be performed with using less force.

After the funnel 251 has been lowered, it is preferably restrained byform-locking means at the sleeve 253. For increased protection, it maybe possible to weld the funnel 251 to the sleeve 253 by using a suitableunder-water welding technology.

The purpose of the support construction is to arrange a substantiallystable position for the funnel structure 250. The funnel structure 250must bear the forces and resist the mass flow from the restricted stream110 from the blowout location 102. In addition, there may be marinecurrents and the like on the seabed 101. The support construction istherefore preferably so dimensioned that it remains firmly in place.

FIGS. 7 and 8 show a second embodiment of the system. The supportstructure comprises now a first foundation part 750 and a secondfoundation part 750 which may comprise compartments 155 for ballast. Butinstead of implementing the holders for the funnel structure 760 asbeams fitted in holders, they are now implemented as support members 751that run along the first foundation part 750 and the second foundationpart 750. This means that the funnel structure 760 can form-lock thanksto its integrated guiding members 754 with the support members 751.

The advantage of the construction as shown in FIGS. 7 and 8 is that thepotentially difficult installation of the beams 201 can be avoided.However, this construction requires some more accuracy in the relativepositioning between the first foundation part 750 and the secondfoundation part 750 in order for the funnel structure 760 to reallyform-lock to the support construction. The positioning can be madeeasier if the height or width of the support members 751 are adjustable,such as if they can be pulled in or out from the first and secondfoundation part 750.

FIG. 9 shows a further embodiment of the system. The exit pipe 301 maybe in the funnel structure 950 on one side. This means that the sleeve953 may be adapted to redirect the stream 110. This embodiment wouldwork with the embodiment shown in FIG. 2 too.

FIG. 10 shows a further embodiment of the system. The funnel 963, 964and the sleeve 961, 962 in the funnel structure comprise now twoseparate parts. The two separate parts can be brought together fromdifferent sides of the blowout location 102. In this manner, the partsof the funnel 963, 964 can be conveniently lowered first and the loweredfunnel can be pushed in place (cf. arrows in FIG. 10) to restrict thespillout location 102. The inventor believes that this kind ofarrangement can substantially reduce the forces required for restrictingthe blowout location 102 since the funnel does not need to be pushedthroughout the stream 110 but the stream 110 is a sort of captured bythe funnel from around, like a manacle.

The funnel structure 250, 950, 961, 962, 963, 964 may also comprisemeans for disjoining an oil pipe. Suitable means include but are notlimited to a mechanical saw, and drilling or cutting tools. The upperend of the pipe may be removed from above the sleeve or from the side ofthe sleeve, depending on the location of the exit pipe 301. The removalis preferably carried out at a free location i.e. where the exit pipe301 is not located.

The assembling of the system in great depths, as well as the filling ofthe compartments with ballast, can be carried out by using submarinevessels. The heavier structures can be let fall down from a suitablyequipped marine vessel ship in a controlled manner.

Modifications and substitutions by one of ordinary skill in the art areconsidered to be within the scope of the present invention, which is notto be limited except by the allowed claims and their legal equivalents.

1. A system for controlling a blowout location at an offshore oilfield,comprising: a support construction that is movable next to a blowoutlocation in an offshore oilfield and that can be set to rest in seabed,the support construction comprising: a) a first foundation part and asecond foundation part that are located at a distance from each other;b) support members that are located at a distance from each other; and afunnel structure that is movable along the support members, the funnelstructure comprising connecting members that are form-locking with thesupport members; and wherein: the first foundation part, the secondfoundation part and the support members are so configured that theblowout location can be restricted a) between the first foundation partand the second foundation part and b) between the support members; thefunnel structure a) is movable along the support members from a sideposition to above the blowout location and b) is dimensioned to restrictthe blowout by redirecting flow from the blowout into an exit pipe; andthe funnel structure and the support construction are so dimensionedthat when the funnel structure is located on top of the blowoutlocation, the system remains substantially stable to enable restrictingthe blowout.
 2. A system according to claim 1, wherein: at least one ofthe first foundation part and second foundation part comprises at leastone compartment that is fillable with ballast.
 3. A system according toclaim 1, wherein: the support members are rod-like members around whichthe funnel structure are form-locked.
 4. A system according to claim 1,wherein: the support members run between holders at the first foundationpart and the second foundation part.
 5. A system according to claim 1,wherein: the support members are elongated guide members which form-lockwith the funnel structure.
 6. A system according to claim 1, wherein:each of the support members are arranged to run along the firstfoundation part or the second foundation part.
 7. A system according toclaim 1, wherein: the funnel structure comprises a vertically movablefunnel.
 8. A system according to claim 1, wherein: the system furthercomprises adjusting members to adjust the height of the support membersfrom the seabed.
 9. A method for controlling a blowout location at anoffshore oilfield, comprising the steps of: bringing a system accordingto preceding claim 1 to an offshore oilfield; positioning the firstfoundation part and the second foundation part of the system to rest inseabed at opposite positions around the blowout location; attaching afunnel structure in a form-locked manner to the system at an awayposition from the blowout location; moving the funnel structure alongsupport members of the system until the funnel structure is on top ofthe blowout location; and controlling the blowout location byredirecting flow from the blowout with the funnel structure into an exitpipe.
 10. A method according to claim 9, further comprising the step of:adjusting the height of the funnel structure.
 11. A method according toclaim 9, further comprising the step of: lowering the funnel structureto the blowout location.
 12. A method according to claim 9, furthercomprising the step of: increasing inertia of the system by addingballast to the system.
 13. A method according to claim 9, furthercomprising the step of: anchoring the system to seabed.
 14. A methodaccording to claim 9, further comprising the step of: adding at leastone extension to the first foundation part or to the second foundationpart.
 15. A method according to claim 9, further comprising the step ofbringing the funnel structure together from different sides of theblowout location.